英文:
Use of MPI::MPI_C alias
问题
-
MPI::MPI_CAlias:MPI::MPI_Cis a CMake alias for the MPI (Message Passing Interface) library. Aliases in CMake are a way to provide a more user-friendly and consistent way to refer to dependencies or libraries. In this case,MPI::MPI_Cis an alias for the MPI C bindings library, which is used for parallel and distributed computing.- When you use
MPI::MPI_Cin your CMake project, CMake automatically sets various variables and properties related to the MPI library, such as include directories, library directories, and compile/link flags. This simplifies the process of finding and linking against MPI for your project.
-
Parameters Set by
MPI::MPI_CAlias:- The
MPI::MPI_Calias sets several parameters and variables because it's designed to provide a comprehensive MPI configuration for your project. This includes not only the necessary library and include directories but also additional compiler and linker flags that might be needed to ensure proper MPI functionality. - Some of the parameters set by
MPI::MPI_Cmay include include paths (CMAKE_Fortran_TARGET_INCLUDE_PATH,C_INCLUDES,Fortran_INCLUDES), compiler flags (C_FLAGS,Fortran_FLAGS), and linker flags that specify library directories and runtime paths (-rpath). - These additional settings are intended to ensure that MPI works seamlessly with your project and that it can properly link and execute parallel code.
- The
In summary, the MPI::MPI_C alias is a convenient way to handle MPI dependencies in CMake projects, as it sets a range of necessary parameters and configurations automatically. While it may seem like it sets more parameters than expected, these settings are designed to provide a robust and comprehensive MPI configuration for your project, ensuring that it works correctly in parallel and distributed computing environments.
英文:
I am building ScaLAPACK (commit 7e4e07070a489686287c36ab473d21cf29a54bdd) using CMake (version 3.20.1). The find_package utility is used in CMakeLists.txt to define the libraries, inclusion directories, and flags required to compile with MPI. The ScaLAPACK library is linked with MPI using the alias MPI::MPI_C:
target_link_libraries( scalapack ${LAPACK_LIBRARIES} ${BLAS_LIBRARIES} MPI::MPI_C)
I am building a shared library, so according to CMake default behavior, the resulting DSO should not have any entries in its RPATH. However, the installed library DSO maintains in its RUNPATH the entries:
$ readelf -d ~/opt/scalapack/lib/libscalapack.so | grep RUNPATH
0x000000000000001d (RUNPATH) Library runpath: [/opt/apps/resif/aion/2020b/epyc/software/UCX/1.9.0-GCCcore-10.2.0/lib64:/usr/lib64:/opt/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/lib]
If the library is linked with using the libraries variable MPI_C_LIBRARIES defined by the find_package utility,
target_link_libraries( scalapack ${LAPACK_LIBRARIES} ${BLAS_LIBRARIES} ${MPI_C_LIBRARIES})
then there is no RUNPATH entry in the installed DSO.
Looking further into the Makefiles generated by CMake, I noticed the following differences:
- With alias
MPI::MPI_C:
# File: <build directory>/CMakeFiles/scalapack.dir/DependInfo.cmake
...
set(CMAKE_Fortran_TARGET_INCLUDE_PATH
"/mnt/irisgpfs/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/include"
"/opt/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/include"
)
...
# File: <build directory>/CMakeFiles/scalapack.dir/Dflags.make
...
C_INCLUDES = -isystem /opt/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/include
C_FLAGS = -O3 -DNDEBUG -fPIC -fexceptions
Fortran_DEFINES = -DAdd_ -Dscalapack_EXPORTS
Fortran_INCLUDES = -I/mnt/irisgpfs/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/include -I/opt/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/include
Fortran_FLAGS = -fallow-argument-mismatch -O2 -DNDEBUG -O2 -fPIC -fexceptions
...
# File: <build directory>/CMakeFiles/scalapack.dir/link.txt
/opt/apps/resif/aion/2020b/epyc/software/GCCcore/10.2.0/bin/gfortran -fPIC -fallow-argument-mismatch -O2 -DNDEBUG -O2 -Wl,-rpath -Wl,/opt/apps/resif/aion/2020b/epyc/software/UCX/1.9.0-GCCcore-10.2.0/lib64 -Wl,-rpath -Wl,/usr/lib64 -Wl,-rpath -Wl,/opt/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/lib -Wl,--enable-new-dtags -L/mnt/irisgpfs/apps/resif/aion/2020b/epyc/software/UCX/1.9.0-GCCcore-10.2.0/lib -L/usr/lib64 -L/mnt/irisgpfs/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/lib -shared -Wl,-soname,libscalapack.so.2.2 -o lib/libscalapack.so.2.2.1 @CMakeFiles/scalapack.dir/objects1.rsp -Wl,-rpath,/home/users/gkafanas/opt/openblas/lib64: /home/users/gkafanas/opt/openblas/lib64/libopenblas.so -lpthread -lm -ldl /home/users/gkafanas/opt/openblas/lib64/libopenblas.so -lpthread -lm -ldl /opt/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/lib/libmpi.so
- With variable
MPI_C_LIBRARIES:
# File: <build directory>/CMakeFiles/scalapack.dir/DependInfo.cmake
...
set(CMAKE_Fortran_TARGET_INCLUDE_PATH
)
...
# File: <build directory>/CMakeFiles/scalapack.dir/Dflags.make
...
C_INCLUDES =
C_FLAGS = -O3 -DNDEBUG -fPIC
Fortran_DEFINES = -DAdd_ -Dscalapack_EXPORTS
Fortran_INCLUDES =
Fortran_FLAGS = -fallow-argument-mismatch -O2 -DNDEBUG -O2 -fPIC
...
# File: <build directory>/CMakeFiles/scalapack.dir/link.txt
/opt/apps/resif/aion/2020b/epyc/software/GCCcore/10.2.0/bin/gfortran -fPIC -fallow-argument-mismatch -O2 -DNDEBUG -O2 -shared -Wl,-soname,libscalapack.so.2.2 -o lib/libscalapack.so.2.2.1 @CMakeFiles/scalapack.dir/objects1.rsp -Wl,-rpath,/home/users/gkafanas/opt/openblas/lib64: /home/users/gkafanas/opt/openblas/lib64/libopenblas.so -lpthread -lm -ldl /home/users/gkafanas/opt/openblas/lib64/libopenblas.so /opt/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/lib/libmpi.so -lpthread -lm -ldl /opt/apps/resif/aion/2020b/epyc/software/OpenMPI/4.0.5-GCC-10.2.0/lib/libmpi.so
So it seems that the alias sets some system options that are not necessary.
I have 2 questions:
- What is the alias
MPI::MPI_Cand how it should be used. - Why the alias sets so may parameters when someone might expect that it will set only the variables used to link the ScaLAPACK DSO with MPI.
答案1
得分: 1
我会间接回答你的问题。由于CMake标准化程度很低，我不清楚`MPI::MPI_C`是什么，以及它是否能够正常工作。以下是我使用的方法：
find_package( MPI )
add_executable( ${PROJECT_NAME} ${PROJECT_NAME}.c )
target_include_directories(
${PROJECT_NAME} PUBLIC
${MPI_C_INCLUDE_DIRS} ${CMAKE_CURRENT_SOURCE_DIR} )
target_link_libraries(
${PROJECT_NAME} PUBLIC
${MPI_C_LIBRARIES} )
这是针对单个源文件的，但可以根据你自己的需求进行调整。
英文:
I'll answer your question indirectly. Since CMake is so little standardized, I have no idea what MPI::MPI_C is or whether it can be made to work. Here is what I use:
find_package( MPI )
add_executable( ${PROJECT_NAME} ${PROJECT_NAME}.c )
target_include_directories(
${PROJECT_NAME} PUBLIC
${MPI_C_INCLUDE_DIRS} ${CMAKE_CURRENT_SOURCE_DIR} )
target_link_libraries(
${PROJECT_NAME} PUBLIC
${MPI_C_LIBRARIES} )
This is for a single source file, but it can be adapted to your own uses.
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